Process for the electrolysis and treatment of sulfate liquors.



I E. J. HUNT & W. I. GIDDEN.

PROCESS FOR THE ELEGTROLYSIS AND TREATMENT OF SULFATE LIQUORS.

APPLIQATION FILED MAR.2I, 1914.

Patented Aug. 18, 1914:.

LTQZEUQQ TED ATEg PATENT @FFKCE EDWIN JAMES HUNT, 0F OLDBURY, ANDWILLIAM THOMAS GIDDEN, 0F WARLEY, ENGLAND, ASSIGNORS TO CHANGE & HUNT,LIMITED, OF OLDBURY, ENGLAND.

PROCESS FOR THE ELECTROLYSIS AND TREATMENT OF SULFATE LIQUORS.

Specification of Letters Patent.

Patented Aug. 18, 1914.

Application filed March 21, 1914. Serial No. 826,196. S

To all whom it may concern:

Be it known that we, EDWIN JA ns HUNT and WILLIAM THOMAS GIDDEN,subjects of the King of Great Britain, and residing, respectively, atthe Chemical Works, Oldbury, England, and Abbey Road, \Varley,lVorcestershire, England, have invented an Improved Process for theElectrolysis and Treatment of Sulfate Liquors, of which the following isa specification.

The accompanying drawings which are more or less diagrammatic show acell embodying our improvements.

Figure 1 shows an elevation of the cell, and Fig. 2 a top plan thereof.

In the electrolysis of sulfate solutions especially sulfate of zinc ithas been found that when lead anodes are employed lead is deposited atthe cathode together with the zinc for example, thus considerably reducing the purity and value of the zinc.-

It has always been supposed that thelead found in the deposited metal atthe cathode was derived from lead transported in solution in theelectrolyte and many attempts have been made to manufacture insolubleanodes of substances other than metallic lead.

l/Ve have discovered that the main source of the lead impurity is notlead transported in solution from anode to cathode but is found in solidparticles of lead peroxid detached from the anode and of solid leadsulfate formed in the neighborhood of the anode which passingundissolved into the electrolyte are deposited as lead at the cathode.

According to this invention in theeleotrolysis of sulfate of zincsolution contain ing free sulfuric acid with vertical lead anodes suchfree particles of undissolved lead compounds are prevented fromcontaminating the metal depositing at the ver tical cathode bypreventing their access to the cathode and for this purpose a porousdiaphragm may be interposed between the electrodes or the anodes or thecathodes may be surrounded with porous material.

The function of the diaphragm or porous material which may convenientlyconsist of asbestos cloth is to prevent insoluble lead compounds formedat the anodes from reaching .the cathodes but the diaphragm should besufliciently porous to permit of as free circulation as possible of theliquor so that the electrolyte is substantially the same at the anodeand cathode.

In working if it be found that at any moment the diaphragm is materiallyhindering the resence of free sulfuric acid at the cathode, free acidmay be added and this may be derived from the anode sections of the cellafter separation of the suspended lead compounds. In any case acidliquor may be continuously or intermittently withdrawn from either theanode sections, the cathode, sections, or both, and the electrolyteshould be kept in free movement either by circulation of liquor or bymechanical agitation.

We may add that we are aware that when electrolyzing a solution ofsulfate of zinc and even when a lead anode has been employed it is notin itself new to use a dia phragm. Previously however the diaphragm wasemployed to separate two liquors of different compositions at the twoelectrodes or to permit different reactions in the solutions at theelectrodes while preventing mutual interference. By our invention however a new' result is obtained, viz, in the electrolysis of an acidsolution of sulfate of zinc present at both anode and cathode, a depositof zinc so pure in spite of the use of lead anodes that a largepercentage of free sulfuric acid may be present at the cathode withoutredissolving the deposited zinc.

Although the use of diaphragms has been known for years it is at presentuniversally accepted that lead anodes cannot be employed forelectrolyzing sulfate of zinc solutions with success. We are howeverable to do this owing to our discovery that the main source of leadimpurity consists of solid and not dissolved lead compound.

Acid liquor drawn off from the cell and,

free from suspended lead compounds is employed to treat crude oXid orcarbonate of zinc. After separation from the excess of zinc oXid orcarbonate the neutral or slightly basic solution is then treated to freeit from any iron and manganese which may remain in after treatment withthe zinc oXid. For this purpose the solution is agitated with a quantityof the lead peroxid (dependent on the quantity of ferrous iron ormanganese present) formed by oxidation of the lead anodes duringelectrolysis, and obtained by separation from liquor in the anodecompartment. The liquor from the anode sections may be employeddirectly, without removal of suspended solid matter, for neutralizationby agitation with crude zinc oxid or ca-rbonate in which case thesuspended peroxid will cause partial or complete separation of the ironand manganese according to its amount but we preferably proceed as abovedescribed. This treatment takes place preferably under the influence ofheat; an alkali, or a metallic oxid such as zinc oxid, or a carbonatesuch as carbonate of lime or zinc may be added to complete theseparation.

In all cases liquors so purified may be furtherpurified by treatmentwith metallic zinc or zinc dust to fit them for electrolysis.

In the annexed drawings, 1 is the cell, 2 are lead anodes, 3 cathodes ofsheet zinc or other suitable metal, 4 are the porous diaphragnis ofasbestos cloth adapted to permit free circulation of the liquor, 5 is asupply pipe at the top of the cell for the supply of electrolyte, and 6are run 95 taps at the bottom of the cell.

What we claim is 1. In a process for the electrolysis of a zinc sulfatesolution containing free sulfuric acid by the aid of a lead anode s0conducting the process that free particles of undissolved lead compoundsderived from the anode cannot pass to the cathode while the 2. In aprocess for the electrolysis of a zinc sulfate solution containing freesulfuric acid the combination with a vertical lead anode of meansadapted to prevent solid free particles of undissolved lead compoundsderived from the anode from passing to the cathode While allowingthe'free passage of the electrolyte. 4

3. In a process for the electrolysis of a zinc sulfate solutioncontaining free sulfuric acid by the aid of a lead anode so conductingthe process that free particles of undissolved lead compounds derivedfromtheanode cannot pass to the cathodewhile the electrolyte at bothanode and cathode remains the same and utilizing the peroxid of lead soobtained to fit zinc sulfate liquors for electrolysis.

4. In a process for the electrolysis of a zinc sulfate solutioncontaining free sulfuric acid the combination with a vertical lead anodeof means adapted to prevent solid free particles of undissolved leadcompounds derived from the anode from passing to the cathode Whileallowing the free passage of the electrolyte and utilizing the peroxidof lead so obtained to fit zinc sulfate liquors for electrolysis.

EDWIN JAMES HUNT. WILLIAM THOMAS GIDDEN. lVitnesses:

GEORGE ANDERSON Co'r'rRELL, CHARLES JOHN CO'I'I'RELL.

